track_nested_command_progress.patch

diff --git a/src/backend/postmaster/pgstat.c b/src/backend/postmaster/pgstat.c
index d362e7f7d7..99e4844e6c 100644
--- a/src/backend/postmaster/pgstat.c
+++ b/src/backend/postmaster/pgstat.c
@@ -3016,8 +3016,10 @@ pgstat_bestart(void)
 #endif
 
 	lbeentry.st_state = STATE_UNDEFINED;
-	lbeentry.st_progress_command = PROGRESS_COMMAND_INVALID;
-	lbeentry.st_progress_command_target = InvalidOid;
+	MemSet(&(lbeentry.st_progress_cmds), 0,
+		   sizeof(PgBackendProgressInfo) * PGSTAT_MAX_PROGRESS_INFO);
+	/* Set invalid command index */
+	lbeentry.st_current_cmd = -1;
 
 	/*
 	 * we don't zero st_progress_param here to save cycles; nobody should
@@ -3203,10 +3205,22 @@ pgstat_progress_start_command(ProgressCommandType cmdtype, Oid relid)
 	if (!beentry || !pgstat_track_activities)
 		return;
 
+	Assert(beentry->st_current_cmd >= -1);
+
+	/* The given command is already started */
+	if (beentry->st_progress_cmds[beentry->st_current_cmd].command == cmdtype)
+		return;
+
+	/* The progress information queue is full */
+	if (beentry->st_current_cmd >= PGSTAT_MAX_PROGRESS_INFO - 1)
+		elog(ERROR, "progress information per backends is full");
+
 	PGSTAT_BEGIN_WRITE_ACTIVITY(beentry);
-	beentry->st_progress_command = cmdtype;
-	beentry->st_progress_command_target = relid;
-	MemSet(&beentry->st_progress_param, 0, sizeof(beentry->st_progress_param));
+	beentry->st_current_cmd++;
+	MemSet(&(beentry->st_progress_cmds[beentry->st_current_cmd]),
+		   0, sizeof(PgBackendProgressInfo));
+	beentry->st_progress_cmds[beentry->st_current_cmd].command = cmdtype;
+	beentry->st_progress_cmds[beentry->st_current_cmd].target = relid;
 	PGSTAT_END_WRITE_ACTIVITY(beentry);
 }
 
@@ -3223,11 +3237,11 @@ pgstat_progress_update_param(int index, int64 val)
 
 	Assert(index >= 0 && index < PGSTAT_NUM_PROGRESS_PARAM);
 
-	if (!beentry || !pgstat_track_activities)
+	if (!beentry || !pgstat_track_activities || beentry->st_current_cmd < 0)
 		return;
 
 	PGSTAT_BEGIN_WRITE_ACTIVITY(beentry);
-	beentry->st_progress_param[index] = val;
+	beentry->st_progress_cmds[beentry->st_current_cmd].params[index] = val;
 	PGSTAT_END_WRITE_ACTIVITY(beentry);
 }
 
@@ -3245,7 +3259,8 @@ pgstat_progress_update_multi_param(int nparam, const int *index,
 	volatile PgBackendStatus *beentry = MyBEEntry;
 	int			i;
 
-	if (!beentry || !pgstat_track_activities || nparam == 0)
+	if (!beentry || !pgstat_track_activities || nparam == 0 ||
+		beentry->st_current_cmd < 0)
 		return;
 
 	PGSTAT_BEGIN_WRITE_ACTIVITY(beentry);
@@ -3254,7 +3269,8 @@ pgstat_progress_update_multi_param(int nparam, const int *index,
 	{
 		Assert(index[i] >= 0 && index[i] < PGSTAT_NUM_PROGRESS_PARAM);
 
-		beentry->st_progress_param[index[i]] = val[i];
+		beentry->st_progress_cmds[beentry->st_current_cmd].params[index[i]] =
+			val[i];
 	}
 
 	PGSTAT_END_WRITE_ACTIVITY(beentry);
@@ -3274,13 +3290,18 @@ pgstat_progress_end_command(void)
 
 	if (!beentry)
 		return;
-	if (!pgstat_track_activities
-		&& beentry->st_progress_command == PROGRESS_COMMAND_INVALID)
+
+	if (!pgstat_track_activities || beentry->st_current_cmd < 0 ||
+		beentry->st_progress_cmds[beentry->st_current_cmd].command ==
+		PROGRESS_COMMAND_INVALID)
 		return;
 
 	PGSTAT_BEGIN_WRITE_ACTIVITY(beentry);
-	beentry->st_progress_command = PROGRESS_COMMAND_INVALID;
-	beentry->st_progress_command_target = InvalidOid;
+	beentry->st_progress_cmds[beentry->st_current_cmd].command =
+		PROGRESS_COMMAND_INVALID;
+	beentry->st_progress_cmds[beentry->st_current_cmd].target =
+		InvalidOid;
+	beentry->st_current_cmd--;
 	PGSTAT_END_WRITE_ACTIVITY(beentry);
 }
 
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 05240bfd14..76ae2e0115 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -495,6 +495,7 @@ pg_stat_get_progress_info(PG_FUNCTION_ARGS)
 		Datum		values[PG_STAT_GET_PROGRESS_COLS];
 		bool		nulls[PG_STAT_GET_PROGRESS_COLS];
 		int			i;
+		int			cmdidx;
 
 		MemSet(values, 0, sizeof(values));
 		MemSet(nulls, 0, sizeof(nulls));
@@ -510,7 +511,18 @@ pg_stat_get_progress_info(PG_FUNCTION_ARGS)
 		 * Report values for only those backends which are running the given
 		 * command.
 		 */
-		if (!beentry || beentry->st_progress_command != cmdtype)
+		if (!beentry)
+			continue;
+
+		/* Look up the progress information of the given command */
+		for (cmdidx = 0; cmdidx <= beentry->st_current_cmd; cmdidx++)
+		{
+			if (beentry->st_progress_cmds[cmdidx].command == cmdtype)
+				break;
+		}
+
+		/* Skip if the command is not running */
+		if (cmdidx > beentry->st_current_cmd)
 			continue;
 
 		/* Value available to all callers */
@@ -520,9 +532,9 @@ pg_stat_get_progress_info(PG_FUNCTION_ARGS)
 		/* show rest of the values including relid only to role members */
 		if (has_privs_of_role(GetUserId(), beentry->st_userid))
 		{
-			values[2] = ObjectIdGetDatum(beentry->st_progress_command_target);
+			values[2] = ObjectIdGetDatum(beentry->st_progress_cmds[cmdidx].target);
 			for (i = 0; i < PGSTAT_NUM_PROGRESS_PARAM; i++)
-				values[i + 3] = Int64GetDatum(beentry->st_progress_param[i]);
+				values[i + 3] = Int64GetDatum(beentry->st_progress_cmds[cmdidx].params[i]);
 		}
 		else
 		{
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index fe076d823d..b87f253777 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -953,13 +953,14 @@ typedef enum
  */
 typedef enum ProgressCommandType
 {
-	PROGRESS_COMMAND_INVALID,
+	PROGRESS_COMMAND_INVALID = 0,
 	PROGRESS_COMMAND_VACUUM,
 	PROGRESS_COMMAND_CLUSTER,
 	PROGRESS_COMMAND_CREATE_INDEX
 } ProgressCommandType;
 
 #define PGSTAT_NUM_PROGRESS_PARAM	20
+#define PGSTAT_MAX_PROGRESS_INFO	4
 
 /* ----------
  * Shared-memory data structures
@@ -1010,6 +1011,18 @@ typedef struct PgBackendGSSStatus
 
 } PgBackendGSSStatus;
 
+/*
+ * Struct for command progress information of one command. The 'target'
+ * should be the OID of the relation which the command targets (we assume
+ * there's just one, as this is meant for utility commands), but the
+ * meaning of each element in the params array is command-specific.
+ */
+typedef struct PgBackendProgressInfo
+{
+	ProgressCommandType command;
+	Oid			target;
+	int64		params[PGSTAT_NUM_PROGRESS_PARAM];
+} PgBackendProgressInfo;
 
 /* ----------
  * PgBackendStatus
@@ -1085,17 +1098,16 @@ typedef struct PgBackendStatus
 	char	   *st_activity_raw;
 
 	/*
-	 * Command progress reporting.  Any command which wishes can advertise
-	 * that it is running by setting st_progress_command,
-	 * st_progress_command_target, and st_progress_param[].
-	 * st_progress_command_target should be the OID of the relation which the
-	 * command targets (we assume there's just one, as this is meant for
-	 * utility commands), but the meaning of each element in the
-	 * st_progress_param array is command-specific.
+	 * Command progress reporting. Since it's possible to nested call
+	 * multiple commands that support progress report, e.g. CLUSTER
+	 * executes REINDEX inside, we track progress of multiple commands.
+	 * st_current_cmd is the index of st_progress_cmds of current executing
+	 * command, -1 for invalid. Any command which wishes can advertise
+	 * that is is running by increasing st_current_cmd and setting
+	 * the corresponding elements of st_progress_cmd.
 	 */
-	ProgressCommandType st_progress_command;
-	Oid			st_progress_command_target;
-	int64		st_progress_param[PGSTAT_NUM_PROGRESS_PARAM];
+	int			st_current_cmd;
+	PgBackendProgressInfo st_progress_cmds[PGSTAT_MAX_PROGRESS_INFO];
 } PgBackendStatus;
 
 /*